Influence of Lewis acids on the symmetric S N 2 reaction

This paper presents a theoretical analysis the effect of non-covalent interactions (NCI) in three different S N 2 reactions (X – :CH 3 X → XCH 3 :X – , X = Cl, Br and I) has been theoretically analysed in the pre-reactive complexes, TS and products. A total of eighteen Lewis acids (LAs: FH, ClH, FCl, I 2 , SeHF, SeF 2 , PH 2 F, PF 3 , SiH 3 F, SiF 4 , BH 3 , BF 3 , BeH 2 , BeF 2 , LiH, LiF, Au 2 and AgCl) interact with the halogen atom of the CH 3 X molecule. To analyse the strength of the non-covalent interactions, both the independent gradient model tool and electron density maps have been employed. The results reveal that in all cases, the interaction between the anion and the Lewis acid leads to an increase in the transition barriers compared to the parental reaction.